Above-ground Arthropod Fauna In Rice Fields And The Exposure Of The Major Species To Bt Protein

The potential effect on non-target organisms(NTOs)is an important aspect in risk assessment of an insect-resistant transgenic crop.For assessing the impact of genetically modified crops on NTOs under laboratory conditions,the surrogate species have to be firstly selected since it is impossible to test all the species in practice.The selected arthropod species should be representative of valued taxa or functional groups in agroecosystem such as predators,parasitoids and pollinators.In addition,since the species that are highly exposed to the insecticidal protein expressed by transgenic crops in the fields are more likely to be negatively affected,they are normally selected as surrogate species.With the aim of selecting proper surrogate species for use in enviromental risk assessment of insect-resistant transgenic rice,the above-ground arthropod species were screened based on the previous studies that occurs in the rice growing regions of Southern and Center China,and a preliminary database were built;furthermore,the major arthropod species were collected in Bt rice,T2A-1,fields and the Cry protein content in them were measured using ELISA.The major results are described as followed:(1)Above-ground arthropod species occurred in rice fields of Southern and Central ChinaA total of 433 arthropod species were screened based on the prvious published data including 131 species of herbivores,181 species of predators and 119 species of parasitoids.Among the species,130 species are arachnids(29.8%);109 species are Hymenoptera(25.2%);46 species are Coleoptera(10.6%);33 species are Diptera(7.6%);32 species are Lepidoptera(7.4%);32 species are Homoptera(7.4%);27 species are Hemiptera(6.2%);16 species are Orthoptera(3.7%);3 species are Thysanoptera(0.7%);3 species are Odonata(0.7%);2 species are Neuroptera(0.5%);1 species is Mantodea(0.2%).There are 123 species that were identified as dominant speices.(2)Cry2Aa concentration in the important arthropods collected from Bt rice fieldsOur ELISA results indicated that the content of Cry2Aa protein in different phytophagous arthropod species are significantly different,though they all feed on rice plant tissues.Some species contain considerable amounts of Cry protein,while some species do not contain at all.Among the phytophagous species detected,the Dipteran species such as Hydrellia griseola(Fallen),contains the highest level of Cry protein;White-backed planthopper and brown planthopper with similar feeding habit both belonging to Delphacidae,while Cry2Aa protein contents in brown planthoppers were significantly higher than in white-backed planthoppers.Cry2Aa concentrations in predatory arthropods collected during anthesis,such as Pirata subpiraticus(Bosenberg et Strand),Marpissa magister(Karsch),Propylaea japonica(Thunberg),Paederus fuscipes Curtis,were significantly higher than in the corresponding arthropods collected after anthesis.Especially,the content of Cry2Aa in the ladybird beetle,P.japonica(Thunberg),was detected 392.4 ng/g dry weight when they collected during rice anthesis,while on Cry2Aa was detected in P.japonica collected after anthesis.The results might imply that during Bt rice anthesis,these species directly ingest lots of Cry protein by feeding on Cry protein-contained rice pollen.However,after rice anthesis they indirectly ingest less or no Cry protein by feeding on their preys.No Bt protein was detected in all the collected parasitods,the result was consistent with the previous studies.In summary,a database of above-ground arthropod species in rice-growing regions of Southern and Center China was preliminarily built.Furthermore,the exposure of the major arthropod species to Cry protein in Bt rice fields were identified.These data provide a scientific basis for selecting appropriate nontarget arthropods as surrogates used in risk assessment of insect-resistant transgenic rice.